The delivery of radio frequency (RF) energy to target regions within solid tissue is known for a variety of purposes of particular interest to the present invention. In one particular application, RF energy may be delivered to diseased regions (e.g., tumors) for the purpose of ablating predictable volumes of tissue with minimal patient trauma.
RF ablation of tumors is currently performed using one of two core technologies. The first technology uses a single needle electrode, which when attached to a RF generator, emits RF energy from an exposed, uninsulated portion of the electrode. The second technology utilizes multiple needle electrodes, which have been designed for the treatment and necrosis of tumors in the liver and other solid tissues. U.S. Pat. No. 6,379,353 discloses such a probe, referred to as a LeVeen Needle Electrode™, which comprises a cannula and an electrode deployment member reciprocatably mounted within the delivery cannula to alternately deploy an electrode array from the cannula and retract the electrode array within the cannula. Using either of the two technologies, the energy that is conveyed from the electrode(s) translates into ion agitation, which is converted into heat and induces cellular death via coagulation necrosis. The ablation probes of both technologies are typically designed to be percutaneously introduced into a patient in order to ablate the target tissue.
Following ablation of the target tissue, a transition zone, also described as a hemorrhagic ring, may remain between the dead ablated tissue and live tissue. Over time, the cells in the transition zone may die, or they may continue to live. Should the cells in the transition zone live, there is a risk that the cells carry the same disease as the ablated tissue and thus perpetuate the disease in healthy tissue. Without any preventative treatment, the diseased cells, and any healthy tissue to which the disease spreads, may require one or more follow-up ablation treatments.
To treat any remaining diseased cells, it is known in the art, for example, to follow an ablation procedure with additional treatment in the form of an ingested pharmaceutical agent. These ingested agents, however, circulate the body to locate any remaining diseased tissue, instead of being directly applied to the diseased tissue. This may delay treatment of the diseased tissue, in addition to possibly exposing healthy tissue to the pharmaceutical agent, which may have a toxic effect on the healthy tissue. Additionally, the pharmaceutical agent may be expelled from the body before the cells in the transition zone develop into diseased cells. It is also known in the art to follow an ablation procedure with an additional procedure in which a pharmaceutical agent is directly deposited in the ablated tissue region. However, depositing the pharmaceutical agent into the ablated tissue region would require focusing deposition of the pharmaceutical agent within the hemorrhagic ring, which may be difficult and burdensome to perform without killing healthy tissue. Furthermore, both examples comprise extra procedures in addition to the ablation procedure that may increase patient trauma.
Therefore, there is a need for preventing tissue surrounding an area of ablated tissue from developing into diseased tissue. There is also a need for treating tissue in conjunction with an ablation procedure to minimize the need for further ablation procedures.